激光测距仪网络摄像头 DIY Python

Question

在网上搜索 DIY 激光测距仪网络摄像头之后；我找到了一个很酷的项目，它以厘米为单位找到激光的距离。我想知道是否有人可以帮助我更改一些代码行，以便它可以用小数来测量以码为单位的距离（就像分数一样）。这是我找到的网站 link webcam laser rangefinder

我对三角学一无所知，除了我记得的高中代数和几何外，我一无所知。换句话说，我不明白这个 link 所讲的数学；这就是为什么，我要求某人向我展示一个代码示例，如果它以码而不是厘米为单位进行测量，代码会是什么样子。提前谢谢你。

这是代码

     ## program written by Shane Ormonde 7th sept 2013
     ## updated on 25th January 2014
     ## calculates the distance of a red dot in the field of view of the webcam.

    import cv2
    from numpy import *
    import math

    #variables
    loop = 1

    dot_dist = 0

    cv2.namedWindow("preview")
    vc = cv2.VideoCapture(1)



    if vc.isOpened(): # try to get the first frame
    rval, frame = vc.read()

    else:
            rval = False
     #print "failed to open webcam"


    if rval == 1 :

           while loop == 1:
        cv2.imshow("preview", frame)
        rval, frame = vc.read()
        key = cv2.waitKey(20)
        if key == 27: # exit on ESC
            loop = 0
        num = (frame[...,...,2] > 236)
        xy_val =  num.nonzero()

        y_val = median(xy_val[0])
        x_val = median(xy_val[1])

        dist = ((x_val - 320)**2 + (y_val - 240)**2 )**0.5 # distance of dot from center pixel
        dist = abs(x_val - 320) # distance of dot from center x_axis only

        print " dist from center pixel is " + str(dist) 

        # work out distance using D = h/tan(theta)

        theta =0.0011450*dist + 0.0154         
        tan_theta = math.tan(theta)



        if tan_theta > 0: # bit of error checking
            obj_dist =  int(5.33 / tan_theta)


        print "3[12;0H" + "the dot is " + str(obj_dist) + "cm  away"
        elif rval == 0:
          print " webcam error "

Answer 1

假设码=厘米*0.010936

更改此块：

if tan_theta > 0: # bit of error checking
    obj_dist =  int(5.33 / tan_theta)

为此：

if tan_theta > 0: # bit of error checking
    obj_dist =  int(5.33 / tan_theta)
    #convert from centimeters to yards
    obj_dist = obj_dist * 0.010936

如果我们查看它告诉我们点有多远的部分，我们会看到 print "3[12;0H" + "the dot is " + str(obj_dist) + "cm away" 行。这告诉我们距离存储在变量 obj_dist 中。所以我通过代码回头看看 obj_dist 是如何得到它的值的。唯一一次引用 obj_dist 是在线：obj_dist = int(5.33 / tan_theta)。查看该行的另一种方法是 obj_dist = centimters_away。所以要得到码，我们所要做的就是添加一条线，将 obj_dist 从厘米转换为码，这就是我所做的。

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